in the large scope of things, we stole this land about 220 years ago... thats not many generations back
Not really.
In the large scope of things (primarily) European settlers took this land by force starting 500 years ago.
That is how humans have been claiming territory since Homo Erectus. It's nothing new and far from the first time a more power group took resources from a less powerful group.
Not unlike the previous land acquisition's of the Aztec, Huns, Persians, Goths, Romans, etc, etc, etc over less powerful groups.
If Mexicans want this land, they can do like humans have been doing for millions of years and try to take it.
Let's also not forget Native American's themselves weren't exactly all meeting up in Utah and singing Kumbaya with each other. They were fighting each other for resources long before a dirty white man even dared to think that the end of the oceans weren't a chasm into the abyss.